Civic VX cant get over 41ish MPG
 

I bought and tuned up a 92 VX with 233xxx miles on it. I put brand new tires on it which are the correct size at 40 PSI. brand new o2 sensor, the correct spark plugs/wires, cap and rotor, all new seals, factory intake with new filter, new brakes...yadda yadda yadda. I am a honda guy and i am very familiar with theses cars but I cant seam to get past the 40ish MPG range.

I drive this car 60 miles one way, mostly highway to work everyday. Ive put 3200 miles on it all averaging 41 MPG.

How can I get this this to do better? am I missing something? It does go into lean burn mode, I can feel it but I have no instrumentation to watch

We need more information.

How fast do you drive? How many times do you use your brakes in a single commute? What sort of terrain? How many miles / gallons since you finished fixing it? Manual or automatic transmission? Average temperatures?

I live in central to western PA so its all smooth pavement but rolling hills. I drive between 55-65 and coast in neutral as much as physically possible. accelerate smoothly using ~75% throttle until i reach 55-60 MPH. Its a 5 speed manual car with d15z1 lean burn vtec e motor. I have driven 3200 miles with about 82 gallons used according to my fuelly account. I rarely use the brakes and use the look a head method as much as possible minus the necessary stop lights.

You should be getting much better mileage than that. I suggest checking compression, preferably with a leakdown tester. If you are losing compression, the leakdown tester tells exactly where it is leaking. Also check the cam timing.

Have checked for brakes dragging or excessive rolling friction? Nothing should be hot after a highway run followed by light braking to a stop.

Ultragauge / Scangauge is your friend.

the car is OBD1, scanguage and ultraguage will not work.

brakes are perfect and brand new, no dragging. I also just did the timing belt and water pump so I know for a fact the mechanical timing is correct but i have not put a timing light on it yet to verify distributor timing

Advanced timing, warm air intake, kill-switch, vacuum gauge, grill block, belly pan, rear wheel skirts, interior mirrors, the list goes on...

There are a lot of options out there to getting higher mpg. What are you willing to do? Do you have a long term mpg goal?

Well I know this little vx is plenty capable in stock form to get at least 50 mpg especially the way I drive it. I still am hesitant to spend any money on instramentatoin until I can prove this car worthy to keep considering I have a crx that averages 38 mpg as is. I bought this car not knowing it was a lemon until I had already was forced to sink $1000 into just to get it into a position that I could possibly drive it or sell it if I had to. I have to be missing something if I can't get into the 50's. I am leaning towards leaking or clogged injectors or I just totally suck at driving in lean burn mode. Any advise for staying in lean burn? I know the hx civics had some tricks dealing with higher rpms around 2000 or 2500 or something. I just don't know the tricks of this vx yet I guess. It runs great though otherwise. Very healthy and reliable. I drive it 120 miles per day and recently drove it on a 750 mile round trip without issue. I just can't get more than my current best 44 mpg

Don't feel bad I'm in same boat but haven't sank much into it yet. Hooked up multimeter to watch lean burn hopefully this tank is better. You'll be amazed 4th on freeway seems to sometimes be better. I have rolling hills though. All you have to do is let of throttle and very gently apply and seems as if I'm then in leanburn. Good luck.

What speeds and rpm are you running in 4th on the highway? At 55 in 5th I'm at roughly 1900 rpm. I know vx's had two different transmissions geared slightly differently

Does that engine have a distributor? That kind of MPG would be consistent with timing retarded 5 or more degrees. Especially look at the vacuum advance. If the vacuum advance is messed up, the engine will develop full power, but get lousy MPG at part throttle.

He's doing the right thing by first getting the car to run the way it should.

It does have a distributor. I haven't pulled out my timing let yet but ill check. I assumed based on its current position it was set decently but ill double check. I'm not sure why I never did check now that I think about it.

Yes the car has a distributor but no vacuum advance. Lol. I have the cx vx trans in both cars. At 65 on freway I'm at like 2100. It is all about getting everything else correct first. And I have herd it said many times a cx will out preform a vx if your not maximizing leanburn.

Is that in 5th gear? If it is that's right about where my car runs. I don't have any instrumentation yet so I can only tell if I'm in lean mode by the butt dyno

Get an MPGuino, about $50. Works on VX and HX and just about any car with fuel injection and a modern type VSS. Read about it in the Instrumentation forum - see the MPGuino subforum there.

Good luck with the VX. Hmmm. Correct weight thin oil in engine and tranny? Put tires up to sidewall max pressure. Pop off the AC belt, see if compressor is starting to freeze up (spin pulley by hand to test). Happened to me but it made the belt squeal, that's how I discovered it.

Your new tires will need some time to break in. Hopefully they have a nice smooth highway tread.

Yes 65 5th gear 2100 ish.

Did you really mean throttle, or do you mean engine load? I get to 75% engine load with about 25% throttle, maybe 30%. If you meant "throttle" you are really stomping on the accelerator. How are you judging throttle position (or load, even)?

Stop putting it in Neutral, your engine cuts fuel any time it's over about 1,200 RPM in gear with the clutch engaged, so by putting it in neutral you are using fuel to keep the engine turning.

It's almost impossible to find Low Rolling Resistance tires in the stock tire size, so that right there is going to give you a small hit in mileage, but my VX has 233,000 miles as well with non LRR tires and I'm getting 47mpg or better with mostly short trips.

Ethanol in your fuel will also kill your mileage in the VX, the higher price of Premium should be offset enough by the increased mileage to make it worth while, if it doesn't you are only out a buck or two.

Thermostat, there is a ~180F and a ~192F thermostat that most auto part stores carry, they are both listed as stock parts, the 192F is the proper stock part.

Stock sized exhaust will extend the life of the o2 sensor and help with mileage.

Some VX's had piles of dealer options like mud flaps, A/C, passenger side mirror... each one of those hurts your mileage a little.

Motor oil, 0W 30 works great in the engine! it also works great in the transmission, the transmission takes regular motor oil, NEVER GL5 gear oil, owners manual tells you to change transmission oil every other year, I have 0w30 and let it go longer because it's synthetic, but I haven't found anyone who's selling a Honda civic who remembers changing the transmission oil, so there is a possibility it's 20 years old!

JRMichler;

After buying my civic last October, I too suspected I was getting less than stock mpg, with relatively "mild" hypermiling I was finding it hard to hit 30. Since I've had em I've done everything in my knowledge base to keep him in top shape regardless of cost.. But anyways, thank you for the info you put into this thread, I am going to check into these things on my car as well, maybe it'll be good for a little improvement.

thanks everyone for the replies. I have found my problem.

The civic is totally stock including stock sized exhaust, no mud flaps. I do use 5w 30 oil however.

I did pull out my timing light before heading to work this morning and found my timing was way retarded, literally and figuratively. I can tell a huge difference. Before I was having trouble keeping the car in lean burn when climbing very slight up hill grades. Now i have no issues and the car seems to transition into lean much smoother. I just filled up the tank yesterday so it will be two days before I have real numbers to compare but I can definitely feel a difference and i believe my problems and quest to 50 MPG have been solved

Thanks guys

Woohoo! Congrats on puttin' er right. Now onward to level 5 VX power!

I gotta tell ya, I'm feeling a bit of lean burn envy.

Oh, and I noticed you were in the PA area. Have you come across this thread?

http://ecomodder.com/forum/showthrea...hip-25691.html

so i spoke too soon. My MPG's have gotten slightly better but i am only at 44 ish MPG now rather than 40-41.

any ideas?

Have you been keeping it in gear while slowing down and using premium/non ethanol gasoline?

What size/type of tires do you have?

I coast in neutral on long down hill sections. I have multipe down hill sections in my daily commute that are over 2 miles long each. I do slow down in gear. I have tried eocing but I'm not a fan of it since my vss and odometer don't work with the key off. I don't want to do any mods until I can get the car to meet the epa estimates. I'm running 175/70/13 tires at 48 psi and you cannot buy non ethanol gas within a 100 mile radius of where I live

This is why I'm so puzzled. I feel like I'm doing everything right. I should by all means be able to get 50 mpg without a mpgurio or mods with my vx in stock form

Sorry your meeting with frustrations... BUT you are getting FE numbers that would be great if you were driving very well in a Civic that does not have lean burn, so I think you are not getting into--or staying in--lean burn mode. In post #17 I asked a question about your throttling that I don't think you've answered yet, but it might have the key to your problem. Might. Are you really hitting the throttle to 75% on each of your accelerations? That seems like hard tramping on the pedal. Pulse and glide on the freeway would keep you out of lean burn too, I believe, from what I have read. Also, reconsider thinking of gauges as mods, if that's what you're doing. If there is some way to get AFR data in your OBD1 vehicle, take it. That would be the easiest way to know if you're in lean burn. I think your hilly environment might also mean it is hard for you to get into lean burn--again because of throttling. Others who actually own and drive these cars can correct me as needed...

Either put it back in to 5th gear and take your foot off the gas or turn the key back one (and only one!) click so the engine turns off, count to 3 then turn it back till the dash lights turn on you will have speed and odometer back, make sure at this point that the tac is reading -0- (if the tac jumps up, try again) if you do this then you will use no gas at all over those 2 miles, as it is you are using gas to keep the engine moving, the engine is doing nothing but sitting there for 2 miles burning gas, if you are going 60mph then this is like letting the car sit in your drive way idling for 2 minutes if you are only going 30mph then it's like starting you car up, going back inside to make a cup of tea and drinking half that cup of tea! at the very least put it back in 5th gear and take your feet off all pedals.

Try Premium and see if it's just not labeled as 100% gasoline, but the ethanol in the gas is killing your mileage by as much as 15%, also try checking at other gas stations or asking at motorcycle shops because older 2 stroke motorcycle engines will burn holes in pistons with Ethanol
Your tires are also wider then stock, if they are not low rolling resistance tires then they are wider then stock tires that are higher drag then stock do you have two hurdles to get over, getting LRR tires will also help get you up to/over 50mpg even if they are in that wide/heavy size.

This last tank I used premium and saw 44 mpg. I can't buy tires Skinnier than 175 anywhere around me and I tried. The tires on it are brand new so I won't be swapping them out anytime soon. Sounds to me like I don't have a choice, either deal with this kind of mileage or start modifying the car and go to what I consider extreme hypermilaging techniques, ie eoc

I also just filled up again and noticed i had one rear tire down to 25ish psi and both fronts were around 35 so i pumped them all back up.

Just picked up my VX from the body shop. It has been down for almost 2 weeks getting all the rust removed. Hopefully i can get some better MPG numbers this week.

http://i257.photobucket.com/albums/h...psb8e0a8f1.jpg

looks beautiful man! no slam that thing on the ground! haha. but yah, with my hx i couldnt get that thing over like 41 until i got an mpguino. from then on ive been getting no lower then 47 mpg. its worth the investment. it will pay its self off in 3 tanks.

Looks nice. Hook up a mpguino or even a volt meter to the 02 and you'll see how to keep it in lean burn. It's the secret. Until I figured it out I was at the 40-45 mark. Sometimes you need to be in 4 th on the freeway to keep the lean burn. It's pin d14 and d16. Orange with stripe and blue with a stripe I believe. There is a lengthy post on how to do it. Good luck. what rpms are you turning on freeway at say 65? 2000-2100 them you at least have the right trans.

Well i took my intake manifold off thinking my EGR passages were clogged. Drilled out and removed the plugs all to find the ports were perfectly clean. So, i drilled and tapped the ports for plugs and reinstalled the intake and cleaned the EGR. I also installed the missing resonating chamber of my stock intake which was missing when I purchased the car and I bought new injectors. I bought a set of 4, Osidetiger's Custom Fuel Injectors off ebay and installed them as well.

First tank out, i hit 47.1 MPG. Im quite happy with these results and will be looking into so instrumentation next.

Thanks everyone for the help.

so your egr wasn't dirty.. seems like the new injectors gave you an extra 7 mpg?

egr had some dirt in it, but not enough to clog it. Im thinking the old injectors were leaking

been doing great, high 40's for the past few weeks

From that May 21st picture it looks like your vx may be missing the rear diffuser that guides air past the rear bumper behind driver's rear wheel. That piece improves aerodynamics (FE). Check for the front pan under the engine compartment, too.

Well I beat my personal best this past week. I drove the car from Pittsburgh to Chicago and back for work averaging in the high 40's until I filled up at a Shell station along the way home.

I managed to pull 56.5 MPG's throughout this tank. I was pretty happy since I set a goal of breaking 50 MPG's without instrumentation.

I beat that goal so I bought an MPGuino! Installed it this weekend and am seeing a $-5 MPG gain on my daily commute while still tinkering with it.

http://i257.photobucket.com/albums/h...ps3e737154.jpg

Thanks for the heads up, my rear panel is there but My front under panel isnt there? My VX looks just like my CRX underneath and i wasnt aware there was an additional front panel? Do you have a parts number or diagram for this?

Its called a splash shield, part numbers 74111SR3A01 or 74000S01A00. There is a diagram at cmsnl.com, but I don't have enough posts on ecomodder to allow me to link it for you.

JCWhitney sells replacements for $40, but I have no experience with them.

Congrats on blasting past your mileage goal.